Stadium: Court 3 (CC) Round: 25 Ground: Clay
| ITF M15 Alkmaar | 2023/06/25 10:00 | Guy Den Heijer v Stijn Paardekooper | 4-6,6-4,12-14 |
| ITF M15 Saarlouis | 2023/06/22 11:30 | Lodewijk Weststrate v Guy Den Heijer | 7-6,6-4 |
| ITF M15 Saarlouis | 2023/06/21 13:20 | David Fix v Guy Den Heijer | 6-4,6-7,2-6 |
| ITF M15 Saarlouis | 2023/06/19 09:30 | Max Wiskandt v Guy Den Heijer | 4-6,2-6 |
| ITF M15 Saarlouis | 2023/06/18 09:00 | Gian Luca Tanner v Guy Den Heijer | 6-3,2-6,8-10 |
| UTR Pro Hilversum | 2023/06/06 06:00 | Guy Den Heijer v Victor Sklenka | 7-6,4-6,5-3 |
| UTR Pro Hilversum | 2023/06/05 07:30 | Guy Den Heijer v Ivan Sergeyev | 0-6,2-6 |
| ITF M15 Antalya | 2023/04/30 07:00 | Guy Den Heijer v Juan Manuel La Serna | 6-7,1-6 |